1. Field of the Invention
The present invention relates to a writing or “drawing” method of a charged particle beam, a generating or “creating” method of writing data, and a computer-readable recording medium with a program recorded thereon. For example, it is related with an electron beam writing method of irradiating electron beams onto a target workpiece while variably-shaping the electron beams, or a generating method of writing data to be input into an electron beam pattern writing apparatus. Alternatively, it is related with a program for embodying these methods.
2. Description of Related Art
Microlithography technology which forwards miniaturization of semiconductor devices is extremely important, because only this process performs forming a pattern in semiconductor manufacturing processes. In recent years, circuit line widths used when writing a desired pattern on semiconductor devices are becoming minute year after year with an increase in high-integration of LSI. In order to form a desired circuit pattern on these semiconductor devices, a high-precision original pattern, such as a reticle or a photomask, is needed. The electron beam writing technology for writing a pattern herein essentially has excellent resolution, and therefore is used for manufacturing such high-precision original patterns.
FIG. 30 shows a schematic diagram for explaining operations of a conventional variable-shaped electron beam pattern writing apparatus. As shown in the figure, the variable-shaped electron beam pattern writing apparatus (EB (Electron beam) writing apparatus) includes two aperture plates and operates as follows. A first aperture 410 has an opening or “hole” 411 in the shape of rectangle, for example, for shaping an electron beam 330. This shape of the rectangular opening may also be a square, a rhombus, a rhomboid, etc. A second aperture 420 has a specially shaped opening 421 for shaping the electron beam 330 having passed through the opening 411 of the first aperture 410 into a desired rectangular. The electron beam 330 that left a charge particle source 430 and has passed through the opening 411 is deflected by a deflector. Then, the electron beam 330 passes through part of the specially shaped opening 421 of the second aperture 420, and reaches a target workpiece 340 mounted on a stage which is continuously moving in one predetermined direction (e.g. X-axis direction) during the writing. In other words, a rectangular shape capable of passing through both the opening 411 and the specially shaped opening 421 is used for pattern writing of the target workpiece 340 mounted on the stage. This method of writing or “forming” a given variable shape by letting beams pass through both the opening 411 and the specially shaped opening 421 is called the “variable shaping.”
In the electron beam writing mentioned above, highly precise critical dimension uniformity is required when writing a pattern on a target workpiece, such as a mask. However, in the electron beam writing, a phenomenon called a proximity effect will occur. In the case of irradiating electron beams onto a mask, where resist is applied, in order to write a circuit pattern thereon, the phenomenon of the proximity effect is generated by backward scattering, meaning that an electron beam penetrates resist film, reaches a layer under the resist film to be reflected, and enters the resist film again. As a result, a pattern is written in dimension deviated from desired one. That is, fluctuation in dimension occurs. On the other hand, when developing the resist film or etching the layer under it after writing a pattern, a dimension fluctuation called a loading effect resulting from the density of a circuit pattern occurs.
As a technique for correcting the proximity effect or the loading effect, the whole circuit pattern is virtually divided into a plurality of small regions, for example, 500 square μm for the global loading effect, 0.5 square μm for the proximity effect, or 50 square nm for the micro loading effect, and a map showing degree of influence is created. It is disclosed, for example, in Published Unexamined Japanese Patent Application No. 2005-195787 (JP-A-2005-195787), that a circuit pattern of a predetermined area density of 50% can be appropriately written and a dose for writing can be calculated using a dose (a fixed value), a map of proximity effect influence values, and a map of proximity effect correction coefficient η calculated from the loading effect correction amount. Moreover, a technique of correcting the loading effect not by correcting a dose but by resizing a pattern dimension in the mask design data beforehand is disclosed, for example, JP-A-2000-75467.
As mentioned above, in the electron beam writing, it has been developed to correct the proximity effect by fluctuating a dose. If it is possible to write a pattern using an isofocal dose, a pattern dimension fluctuation can be prevented even when a height deviation of a target workpiece surface or a focal positional deviation error caused by a lens excitation error etc. occurs at the focal position. However, the optimal dose irradiated in correcting the proximity effect according to the dose change method stated above is not necessarily in accordance with the isofocal dose. Therefore, even when a pattern is written with the optimal dose calculated by proximity effect correction to be in accordance with the dimension of the pattern, if an error arises at the focal position, deviation is generated in each pattern dimension. In other words, in the method of correcting the proximity effect by way of fluctuating the dose, a tolerance to a pattern dimension error caused by a focal positional deviation error is small.